Using a linear quasi-geostrophic model of large scale spiraling flow and vertical density gradient in the eastern North Pacific, we evaluate the complex dispersion relationships for quasi-geostrophic waves. Our calculations indicate that the geostrophic circulation of the eastern North Pacific can locally convert potential energy to mesoscale kinetic energy on a scale comparable to the observed space and time scale and should be a source of eddy energy, distant from the eddies spawned by the Kuroshio and near the topographic features. But the local growth rates by linear stability analysis do not relate to the observed features of eddy kinetic energy in the eastern ocean; eddy kinetic energy increases to the south and has a maximum in the subtropical region. The non-linear baroclinic instability is analyzed using a three-layer quasi-geostrophic numerical model. Three experiments with different idealized initial mean flow are performed. Local energetics are calculated to highlight the difference between the southward return flow and westward return flow regions. It is found that the boundary flux of mean to eddy kinetic energy conversion is the main differences between two regions: it is large in the westward return flow region but is small in the southward return flow region. Two waves with different characteristics are found: the short waves (periods of 120 days), that propagate to the west and form several wave trains parallel to the southern boundary, and the long waves (periods of 200 days), that propagate to the south-west. These two waves are remarkably similar to the measurements of open ocean eddies at 28°N and 152°W. It is shown that there are high eddy activities in the southward return flow regions by influxes of eddies from other areas, but the southward return flow region is vacant in eddies by outflows of the westward and south-westward propagating waves. / Graduation date: 1987

Graduation date: 1969

The frontal system that passed over the Storm Transfer and Response Experiment Study area on 19 November 1980 was the third vigorous system in succession to affect this region of the northeast Pacific Ocean. This study marks the first detailed investigation of a frontal wave over the Gulf of Alaska and as such provides structural details not shown in other studies. Precipitation and changes in temperature, wind velocity, and pressure were associated with the passage of both the warm and cold fronts. The thermal structure exhibits a well defined warm sector with regions of large baroclinicity in both the warm and cold frontal zones. Data from radiosonde releases from the northern-most of two observing platforms indicate a mid-level upper moisture front above the kata cold front. Throughout these northern cross-sections, gradients in the warm and cold frontal zones are of similar magnitudes while sections from the southern ship show a warm frontal zone that is more intense than the cold transition region. Along-frontal gradients of equivalent potential temperature are of the same order of magnitude as the cross-frontal gradients. Horizontal wind components relative to the storm indicate strong inflow to the system at lower layers from both south and east. The wind exits the system to the west and south. Upper level winds are westerly throughout. Gradients of wind components are strongest in frontal zones, which results in the cold front coincident with the peak axis in the vertical component of relative vorticity. The field of horizontal divergence also exhibits its largest magnitudes in the frontal zones, with convergence in the warm frontal zone and divergence in the cold transition region. This seldom observed feature of divergence at the cold front leads to a downwelling motion in this region and categorizes the front as a kata-cold trout. Most of the upward vertical velocity occurs in and around the warm frontal zone as a result of horizontal convergence in this region. Relative isentropic analysis indicates that there are three main air streams within the system. The warm conveyor belt flows to the north in the warm sector and rises gradually as it makes it way to the north. Ahead of the warm front and behind the cold front are two cold air streams that flow to the north and south respectively. Analysis of the kinematic, frontogenesis indicates that confluence and infrequently studied shear effects are the most important processes influencing the frontal gradients. Analysis of uncertainty in the terms of the prognostic kinematic frontogenesis equations reveals that the diabatic heat and twisting terms that others have found important are smaller than their estimated errors in this study. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Graduation date: 1969

Graduation date: 1969

Hydroacoustic tertiary (T-) waves are seismically generated acoustic waves that propagate over great distances in the ocean sound channel with little loss in signal strength. Hydrophone recorded T-waves can provide a lower earthquake detection threshold and an improved epicenter location accuracy for oceanic earthquakes than land-based seismic networks. Thus detection and location of NE Pacific ocean earthquakes along the Blanco Transform Fault (BTFZ) and Gorda plate using the U.S. Navy's SOSUS (SOund SUrveillance System) hydrophone arrays afford greater insight into the current state of stress and crustal deformation mechanics than previously available. Acoustic earthquake information combined with bathymetry, submersible observations, earthquake source-parameter estimates, petrologic samples, and water-column chemistry renders a new tectonic view of the southern Juan de Fuca plate boundaries. Chapter 2 discusses development of seismo-acoustic analysis techniques using the well-documented April 1992 Cape Mendocino earthquake sequence. Findings include a hydrophone detection threshold estimate (M~2.4), and T-wave propagation path modeling to approximate earthquake acoustic source energy. Empirical analyses indicate that acoustic energy provides a reasonable magnitude and seismic moment estimate of oceanic earthquakes not detected by seismic networks. Chapters 3 documents a probable volcanogenic T-wave event swarm along a pull-apart basin within the western BTFZ during January 1994. Response efforts yielded evidence of anomalous water-column ��He concentrations, pillow-lava volcanism, and the first discovery of active hydrothermal vents along an oceanic fracture zone. Chapter 4 discusses the detection of a NE-SW trending microearthquake band along the mid-Gorda plate which was active from initiation of SOSUS recording in August 1991 through July 1992, then abruptly ceased. It is proposed that eventual termination of the Gorda plate seismicity band is due to strain reduction associated with the Cape Mendocino earthquake sequence. Chapter 5 combines bathymetric, hydro-acoustic, seismic, submersible, and gravity data to investigate the active tectonics of the transform parallel Blanco Ridge (BR), along the eastern BTFZ. The BR formation mechanism preferred here is uplift through strike-slip motion (with a normal component) followed by formation and intrusion of mantle-derived serpentinized-peridotite into the shallow ocean crust. The conclusion considers a potential link between the deformation patterns observed along the BTFZ and Gorda plate regions. / Graduation date: 1998

Graduation date: 1998

A long and gradual transition between the summer and winter oceanic regimes was observed off Oregon during the autumn of 1980. Hydrographic sections and a single current meter mooring between August and December show the ocean possessed characteristics during fall that have not been observed during other seasons: a slow ascension of the poleward undercurrent and the appearance of a large bottom boundary layer. The decay of summer's southward surface flow was achieved by a series of modest northward wind events during late summer as the effects of southward winds were becoming diminished. The northward wind events had progressively stronger influence on surface currents. The barotropic current fluctuations that are a signature of the summer regime continued during the transitional period. The weekly-to-monthly averaged flow was barotropic during much of the transition. Hydrographic sections and time series of alongshore current shear and temperature show that the leveling of the frontal layer was achieved gradually over a two month time scale. The winter regime was established during eleven days of continuous northward wind stress in early November. / Graduation date: 1987

No description available.

Graduation date: 1981 / Best scan available. Figures in original are black and white photocopies.